This invention relates generally to the field of sealable containers comprising a main body with a removable lid member, including both primary and secondary containers, wherein the container is provided with means to temporarily and releasably seal the lid member to the main body, such that the lid member can be removed and replaced for access to the interior of the container, and is further provided with means to permanently seal the lid member to the main body by thermo-bonding, such that the lid member and main body become an integral unit. More particularly, the invention relates to such containers comprising an inner body member and inner lid member composed of a thermoplastic polymer material and an outer body member and outer lid member composed of a metal.
There are circumstances where it is desirable to store materials within a container of a type such that the container can be opened and resealed once or multiple times, and later permanently sealed such that the container lid cannot be removed from the container body without destruction of the lid or body. One field where this is particularly desirable is the field of hazardous and/or radioactive waste storage and disposal. Hundreds of millions of tons of hazardous and/or radioactive waste materials are generated each year, such as solid waste in bulk or particulate form, sludge, stabilized waste, medical waste, and radioactive waste. For collection, storage, transport and disposal of such hazardous and/or radioactive wastes, it is common to utilize drums or box containers, made of plastic or metal dependent on the nature of the hazardous and/or radioactive material, where the hazardous material is either placed directly into the containers, such that the containers are designated as primary containers, or the waste is disposed within drums or boxes, and the drums or boxes themselves are then placed within the containers, such that the containers are designated as secondary containers.
One approach to addressing the need for temporary sealing followed by permanent sealing of the container is to provide a container whereby the lid of the container is temporarily secured to the main body of the container by mechanical fastener means, such as a releasable annular drum clamp, with the lid later permanently bonded in some manner to the body of the container to form an integral unit, such that the interior of the container cannot be accessed except by cutting or destroying the container. A container of this type is described for example in U.S. Pat. Nos. 4,586,624 and 4,743,320, the disclosures of which are incorporated herein by reference, wherein a lid made of thermoplastic material is thermo-welded or thermo-bonded to a container made of thermoplastic material by melting the contacting portions of the lid and container.
There are numerous regulations and standards relative to acceptable containers for the transport and storage of different types of hazardous and/or radioactive waste. Macroencapsulation is currently available at facilities permitted by the U.S. Environmental Protection Agency (EPA) for the treatment of radioactively contaminated hazardous waste. Macroencapsulation as specified by the EPA is designed to isolate hazardous waste from the disposal environment. The macroencapsulation process uses inert or non-reactive materials to achieve this isolation. The EPA began developing treatment standards for hazardous wastes in the late 1980's. The EPA developed these treatment standards based on the best demonstrated available technology for broad categories of waste. By 1992, the EPA realized that wastes such as debris were not amenable to the treatment standards established for process wastes. At that time the EPA promulgated alternative treatment standards for debris. They provided several options, one of which was macroencapsulation. The EPA had previously established macroencapsulation as the treatment standard for radioactively contaminated lead solids. The EPA defines macroencapsulation as the application of surface coating materials such as polymeric organics (e.g., resins and plastics) or use of jacket of inert inorganic materials to substantially reduce surface exposure to potential leaching media. The EPA went on to describe a performance standard for macroencapsulation of debris. This performance standard requires that the encapsulating material must completely encapsulate debris and be resistant to degradation by the debris and its contaminants and materials into which it may come into contact after placement (leachate, other waste, microbes).
Certain disposal sites require that the contents of containers brought to the site be verified on site, and the sites will not accept permanently sealed containers of hazardous and/or radioactive waste. In some instances, containers formed of solely of polymeric material do not meet the DOT, NCR, disposal sites, state or UN requirements for a particular type of hazardous and/or radioactive waste. Thus in many instances it is necessary to provide containers or secondary containers that are temporarily sealable to allow visual inspection, and which can then be permanently sealed in some manner for storage.
It is an object of this invention to provide a container that addresses the problems set forth above and that is composed of an outer container formed of a metal in combination with an inner container formed of a thermoplastic material, where the container may be sealed on a temporary basis by releasable and reusable sealing means to allow access to the interior of the inner container, and further where at least the inner container may be permanently sealed by thermo-welding the thermoplastic lid onto the thermoplastic main body. It is a further object to provide such a container where the inner thermoplastic container is either a separable insert received within the outer container or is an insert or liner adhered to the outer container, and preferably where the thermoplastic body is a liner or insert adhered to the interior walls of the outer container body while the thermoplastic lid is separate from the outer container lid or where the inner thermoplastic lid is a liner or insert adhered to the interior of the outer metal lid and the thermoplastic body is a liner or insert adhered to the interior walls of the outer container body. It is a further object to provide such a container where the temporary sealing means is a mechanical interlocking structure, either incorporated into the structure of the container itself or provided as a separate member, and where the permanent sealing means is a thermo-welded bond created by selectively melting the contacting portions of the thermoplastic lid and body, and which preferably utilizes an electrically conductive resistance wire disposed adjacent or embedded in the contacting portion or portions of the thermoplastic lid and body, such that current passed through the wire produces localized heating through resistance effects sufficient to melt portions of the lid and body which upon cooling create an integral container.